A Novel Transport Mechanism for MOMP in Chlamydophila pneumoniae and Its Putative Role in Immune-Therapy

Major outer membrane proteins (MOMPs) of Gram negative bacteria are one of the most intensively studied membrane proteins. MOMPs are essential for maintaining the structural integrity of bacterial outer membranes and in adaptation of parasites to their hosts. There is evidence to suggest a role for purified MOMP from Chlamydophila pneumoniae and corresponding MOMP-derived peptides in immune-modulation, leading to a reduced atherosclerotic phenotype in apoE^−/− mice via a characteristic dampening of MHC class II activity. The work reported herein tests this hypothesis by employing a combination of homology modelling and docking to examine the detailed molecular interactions that may be responsible. A three-dimensional homology model of the C. pneumoniae MOMP was constructed based on the 14 transmembrane β-barrel crystal structure of the fatty acid transporter from Escherichia coli, which provides a plausible transport mechanism for MOMP. Ligand docking experiments were used to provide details of the possible molecular interactions driving the binding of MOMP-derived peptides to MHC class II alleles known to be strongly associated with inflammation. The docking experiments were corroborated by predictions from conventional immuno-informatic algorithms. This work supports further the use of MOMP in C. pneumoniae as a possible vaccine target and the role of MOMP-derived peptides as vaccine candidates for immune-therapy in chronic inflammation that can result in cardiovascular events.     

Glycation of human serum albumin alters its binding efficacy towards the dietary polyphenols: a comparative approach

Diabetes is a major problem in the world. The proteins became modified during glycation after reacting with the reducing sugars (e.g. D-glucose) via non-enzymatic pathways. The glycated analogue of human serum albumin (HSA) has been characterized with the help of multi-spectroscopic methods. It has been observed that six glucose molecules can bind covalently to HSA under experimental condition. The binding affinity of the modified HSA towards the dietary polyphenols has been estimated using UV–vis and fluorescence spectroscopic techniques. The binding constant values of the ligands were found to decrease after the modification of HSA.     

Role of inhibitors in the induction of differentiation in callus cultures of Brassica,Datura and Nicotiana

The effect of various inhibitors on differentiation (shoot morphogenesis) in callus cultures of Brassica, Datura and Nicotiana has been investigated. Hormone medium without any inhibitor (control), resulted in 6% shoot formation. Addition of inhibitors such as actinomycin D, cordycepin, abscisic acid, trigonelline and theophylline greatly enhanced shoot formation. The results suggest that inhibitors play a regulatory role in the control of differentiation.Abbreviations ABA Abscisic acid - BA Benzyl adenine - Kn Kinetin - MS Murashige Skoog's - NAA 1-naphthalene acetic acid     

Role of Two Strictly Conserved Residues in Nucleotide Flipping and N-Glycosylic Bond Cleavage by Human Thymine DNA Glycosylase

Thymine DNA glycosylase (TDG) promotes genomic integrity by excising thymine from mutagenic G·T mismatches arising by deamination of 5-methylcytosine, and follow-on base excision repair enzymes restore a G·C pair. TDG cleaves the N-glycosylic bond of dT and some other nucleotides, including 5-substituted 2′-deoxyuridine analogs, once they have been flipped from the helix into its active site. We examined the role of two strictly conserved residues; Asn¹⁴⁰, implicated in the chemical step, and Arg²⁷⁵, implicated in nucleotide flipping. The N140A variant binds substrate DNA with the same tight affinity as wild-type TDG, but it has no detectable base excision activity for a G·T substrate, and its excision rate is vastly diminished (by ∼10^4.4-fold) for G·U, G·FU, and G·BrU substrates. Thus, Asn¹⁴⁰ does not contribute substantially to substrate binding but is essential for the chemical step, where it stabilizes the transition state by ∼6 kcal/mol (compared with 11.6 kcal/mol stabilization provided by TDG overall). Our recent crystal structure revealed that Arg²⁷⁵ penetrates the DNA minor groove, filling the void created by nucleotide flipping. We found that the R275A and R275L substitutions weaken substrate binding and substantially decrease the base excision rate for G·T and G·BrU substrates. Our results indicate that Arg²⁷⁵ promotes and/or stabilizes nucleotide flipping, a role that is most important for target nucleotides that are relatively large (dT and bromodeoxyuridine) and/or have a stable N-glycosylic bond (dT). Arg²⁷⁵ does not contribute substantially to the binding of TDG to abasic DNA product, and it cannot account for the slow product release exhibited by TDG.     

Daily and Seasonal Rhythms in Immune Responses of Splenocytes in the Freshwater Snake,Natrix piscator

Present study was designed to examine daily and seasonal variability in the innate immune responses of splenocytes in the fresh water snake, Natrix piscator. Animals were mildly anesthetized and spleen was aseptically isolated and processed for macrophage phagocytosis, NBT reduction, nitrite production, splenocyte proliferation and serum lysozyme activity. Samples were collected at seven time points, viz., 0000, 0400, 0800, 1200, 1600, 2000 and 0000 h during three different seasons, namely summer, winter and spring. Cosinor analysis revealed that percent phagocytosis had a significant 24-h rhythm during summer and spring seasons. The peaks of rhythms in NBT reduction and nitrite release occurred in the morning hours at 10.88 h and 8.31 h, respectively, in winter. A significant 24-h rhythm was also observed in lysozyme concentration and splenocyte proliferation (both Basal and Concanavalin A stimulated) in all three seasons. A significant phase shift in splenocyte proliferation was obtained with a trend of delayed phase shift from winter to spring and from spring to summer. Of the nine variables, significant annual (seasonal) rhythms were detected in almost all variables, excluding phagocytic and splenosomatic indices. All rhythmic variables, except spleen cellularity, exhibited tightly synchronized peaks coinciding with the progressive and recrudescence phases of annual reproductive cycle. It is concluded that the snake synchronizes its daily and seasonal immune activity with the corresponding external time cues. The enhancement of immune function coinciding with one of its crucial reproductive phases might be helping it to cope with the seasonal stressors, including abundance of pathogens, which would otherwise jeopardize the successful reproduction and eventual survival of the species.     

Reproductive Phase-Dependent Annual Variation in the Effects of Melatonin and Pinealectomy, with or without Iopanoic Acid/Cyproterone Acetate, in the Regulation of Serum Cholesterol in Clarias batrachus

The present study was aimed at examining the putative thyroid or androgen dependency of the roles of melatonin/the pineal in the regulation of serum cholesterol in a freshwater catfish, Clarias batrachus . During four different phases of the annual gonadal cycle melatonin-treated or pinealectomized fishes received either iopanoic acid or cyproterone acetate or vehicle in the early morning or late afternoon. The results indicate that the effects of melatonin on serum cholesterol appear to be thyroid and testis independent during the preparatory and late postspawning phases. In contrast, the effect of pinealectomy is brought about mainly by way of the thyroid and/or the testis.